Webpack compiling assets on every request - Ruby on Rails 6

I have a problem with Webpack in my Ruby on Rails application. In development pages are loaded very slowly because on every request webpack recompiles the changes:

Started GET "/404" for ::1 at 2020-12-03 15:24:33 +0100
Processing by ErrorsController#not_found as HTML
  Rendering errors/not_found.html.erb within layouts/errors
  Rendered errors/not_found.html.erb within layouts/errors (Duration: 0.6ms | Allocations: 688)
The resolved_paths option has been deprecated. Use additional_paths instead.
[Webpacker] Everything's up-to-date. Nothing to do
The resolved_paths option has been deprecated. Use additional_paths instead.
[Webpacker] Everything's up-to-date. Nothing to do
The resolved_paths option has been deprecated. Use additional_paths instead.
[Webpacker] Everything's up-to-date. Nothing to do
The resolved_paths option has been deprecated. Use additional_paths instead.
[Webpacker] Everything's up-to-date. Nothing to do
The resolved_paths option has been deprecated. Use additional_paths instead.
[Webpacker] Everything's up-to-date. Nothing to do
The resolved_paths option has been deprecated. Use additional_paths instead.
[Webpacker] Everything's up-to-date. Nothing to do
The resolved_paths option has been deprecated. Use additional_paths instead.
[Webpacker] Everything's up-to-date. Nothing to do
The resolved_paths option has been deprecated. Use additional_paths instead.
[Webpacker] Everything's up-to-date. Nothing to do
Completed 200 OK in 1204ms (Views: 1203.4ms | ActiveRecord: 0.0ms | Allocations: 31195)

In development I can fix that by using ruby bin/webpack-dev-server but when running my RSpec tests there is the same problem. On every request, webpack is recompiling the assets and tests are really slow.

My config/webpacker.yml looks like this:

# Note: You must restart bin/webpack-dev-server for changes to take effect

default: &default
  source_path: app/javascript
  source_entry_path: packs
  public_root_path: public
  public_output_path: packs
  cache_path: tmp/cache/webpacker
  check_yarn_integrity: false
  webpack_compile_output: true

  # Additional paths webpack should lookup modules
  # ['app/assets', 'engine/foo/app/assets']
  additional_paths: [
    'vendor/assets'
  ]

  # Reload manifest.json on all requests so we reload latest compiled packs
  cache_manifest: false

  # Extract and emit a css file
  extract_css: true

  static_assets_extensions:
    - .jpg
    - .jpeg
    - .png
    - .gif
    - .tiff
    - .ico
    - .svg
    - .eot
    - .otf
    - .ttf
    - .woff
    - .woff2

  extensions:
    - .mjs
    - .js
    - .sass
    - .scss
    - .css
    - .module.sass
    - .module.scss
    - .module.css
    - .png
    - .svg
    - .gif
    - .jpeg
    - .jpg

development:
  <<: *default
  webpack_compile_output: true

  compile: true

  # Verifies that correct packages and versions are installed by inspecting package.json, yarn.lock, and node_modules
  check_yarn_integrity: true

  # Reference: https://webpack.js.org/configuration/dev-server/
  dev_server:
    https: false
    host: localhost
    port: 3035
    public: localhost:3035
    hmr: false
    # Inline should be set to true if using HMR
    inline: true
    overlay: true
    compress: true
    disable_host_check: true
    use_local_ip: false
    quiet: false
    headers:
      'Access-Control-Allow-Origin': '*'
    watch_options:
      ignored: '**/node_modules/**'


test:
  <<: *default
  compile: true

  # Compile test packs to a separate directory
  public_output_path: packs-test
  check_yarn_integrity: false

production:
  <<: *default

  # Production depends on precompilation of packs prior to booting for performance.
  compile: false

  # Cache manifest.json for performance
  cache_manifest: true

  webpack_compile_output: true

How can I fix that?